Based on the basic characteristics of atmosphere in near space,the interaction between laser and atmosphere was analyzed and studied. The absorption and scattering of atmosphere in near space was analyzed by the MODTRAN software,and the transmittance curve of laser wavelength within 400~2000 nm was given. From laser spot drifting and beam radius expanding,the influence of atmosphere turbulence on laser transmission was calculated,and the threshold power of thermal blooming was estimated. The conclusion show that the influence of atmosphere on laser transmission in near space is weaker than that in terrestrial space,which is helpful to realize the long range transmission of high power laser.